The present invention relates to integrated semiconductor device technology in the field of sensors and radiant sources of electromagnetic energy. More specifically, the present invention relates to a method and structures of the class described in U.S. Pat. Nos. 4,472,239 and 4,478,077. Such devices have applications in areas including flow sensing, detection of combustible gases, humidity sensing, and pressure sensing. However, neither these devices nor the present invention is limited to such applications.
The present invention comprises a semiconductor device and a method for fabricating the semiconductor device.
The present invention comprises a method of fabricating a semiconductor device comprising a thin film member having a predetermined configuration bridging a depression etched into a first surface of a semiconductor body. The member is connected to the first surface at first and second substantially opposing ends of the predetermined configuration. The depression opens to the first surface along an edge on each side of the member. The method comprises the steps of providing a semiconductor body with a first surface having a predetermined orientation with respect to a crystalline structure in the semiconductor body. A layer of thin film material of which the member is comprised is applied onto the first surface. First and second openings are exposed through the thin film material to the first surface. The first opening is bounded in part by one edge of the member. The second opening is bounded in part by the other edge of the member. Both openings are also bounded in part by a boundary connected to an edge of the member. At least one of the boundaries has a predetermined boundary configuration formed so that, when an anisotropic etch is placed on the openings to undercut the member and form the depression, there will be no substantial undercutting of the semiconductor body below the thin film material at the predetermined boundary configuration.
The present invention further comprises an integrated semiconductor device comprising a semiconductor body with a first surface having a predetermined orientation with respect to a crystalline structure in the semiconductor body. The semiconductor body has a depression formed into the first surface of the body. A layer of thin film material covers at least a portion of the first surface. A thin film member comprising the layer of material has a predetermined configuration bridging the depression. The member is connected to the first surface at substantially opposing ends of the predetermined configuration. The depression opens to the first surface along an edge on each side of the member. The layer of thin film material comprises first and second openings, the first opening being bounded in part by one edge of the member, the second opening being bounded in part by the other edge of the member. Both openings are also bounded in part by a boundary connected to an edge of the member. At least one of the boundaries has a predetermined boundary configuration formed so that, when an anisotropic etch is placed on the openings to undercut the member and form the depression, there will be no substantial undercutting of the semiconductor body below the thin film material at the predetermined boundary configuration.
Substantially eliminating undercutting of the semiconductor body below the thin film material at the predetermined boundary configuration substantially eliminates overhang of the thin film material at these locations. Substantially avoiding such overhang is frequently important since such overhang is frequently wasted space on a semiconductor chip. Such area is unavailable for diodes on other electronic structures in the semiconductor body. Further, because of breakage possibilities in handling and processing, thin film conductors such as gold conductors on the order of 0.3-0.5 microns thick cannot be wisely placed there because they add stress to the overhang, which, if it fractures, will cause an open circuit as well as possible mechanical and thermal interference if a fragment is lodged, for example, under the bridged structures of the present invention. In addition, making the openings without substantial overhang facilitates air flow and/or thermal isolation of the bridged member from the semiconductor body. Accordingly, devices in accordance with the present invention avoid wasted space on semiconductor chips, enhance thermal isolation of elements on the bridged member, and result in small, less costly and more reliable chips and devices.